This invention relates to a multi fuel engine control and particularly to such a control of the type in which fuel at a substantially constant pressure is injected in pulses by opening a fuel injector for predetermined pulse durations. Each such pulse duration has a fuel flow portion and a non-flow, injector opening portion. The duration of the fuel flow portion determines the amount of fuel delivered with the pulse, which amount is substantially proportional to the duration.
Such an engine may be operated with a mixture of combustible fuels such as gasoline and methanol. It is known to adjust the injection pulse durations of such engines in response to a fuel composition signal to compensate for the variable volumetric heat content of these fuels; however, such fuels also have different viscosities. The viscosity of the fuel mixture will thus vary with fuel composition as well as with fuel temperature; and the variable viscosity will change the actual fuel delivered through the same injector at a predetermined pressure. With a single calibration of the fuel control based on a predetermined viscosity, the fuel delivered with each pulse will be in error as the fuel composition varies, even if the fuel pulse calculation takes into account the varying volumetric heat content of the fuel mixture.